Manually shifted, non-synchronized, nonblocked, mechanical, constant mesh change gear transmissions, usually for driving a land vehicle from a prime mover such as an Otto cycle or diesel engine, are well known in the prior art. Examples of such transmissions may be seen by reference to U.S. Pat. Nos. 3,105,395; 3,138,965; 3,283,613 and 3,611,823, the disclosures of which are hereby incorporated by reference in their entirety. This type of transmission utilizes selectively engageable positive or jaw clutches. Positive clutches of this type are relatively compact and inexpensive as compared to friction clutches, synchronized clutches and/or blocked clutches and are very reliable if utilized in connection with some type of synchronizing means.
Conventional, individually synchronized and/or blocked positive clutch structures are well known in the prior art as may be seen by reference to U.S. Pat. Nos. 3,221,851; 3,929,029; 4,307,624; 4,497,396; 3,799,002; 4,428,469 and 4,132,122, the disclosures of which are hereby incorporated by reference in their entirety. Conventional individual synchronizing devices, while providing easy shifting of gears in a transmission, require a relatively large space in the transmission housing and, due to the relatively limited space available within a transmission housing, are of a relatively limited capacity and/or life. This is especially true for transmissions utilized with heavy duty vehicles wherein the torque transfer capacities and inertias involved are relatively large. Individual blocked positive clutch assemblies, while providing relatively easy shifting of the transmission, do require a certain degree of skill to cause a crossing of synchronization and further are more complicated and space consuming than a conventional nonsynchronized non-blocked jaw clutch assembly.
Synchronizing of conventional nonsynchronized, nonblocked jaw clutch assemblies by operator manipulation of engine speed and "double clutching," is a highly efficient, well known and widely used transmission shifting method. However, such manual synchronizing of a mechanical transmission requires a high degree of operator skill, effort and attention.
Automatic mechanical transmission systems wherein electronic central processing units are utilized to automatically cause synchronization of positive jaw clutches by automatic manipulation of engine speed and the vehicle master clutch are also known in the prior art as may be seen by reference to U.S. Pat. No. 4,361,060, the disclosure of which is hereby incorporated by reference in its entirety. Such control systems require rather complicated engine and master clutch controls and further, when synchronizing the jaw clutches for a downshift, are limited by the engine governed speed, acceleration, and response times as to speed, acceleration and response time of the transmission input shaft driven jaw clutch members.
Automatic mechanical transmission systems utilizing power synchronizer devices, i.e. devices independent of engine speed, to provide input shaft braking and acceleration, and not manipulation of engine speed, to synchronize the transmission jaw clutch members, are known in the prior art. Examples of such systems may be seen be reference to U.S. Pat. Nos. 3,478,851; 4,023,443; 4,140,031 and 4,614,126, the disclosures of which are hereby incorporated by reference in their entirety.
Automatic mechanical transmission systems having a power synchronizer and also having a torque converter drivingly interposed between a drive engine and the transmission input shaft, and including a torque converter lock-up/disconnect clutch assembly, are known. Examples of such systems may be seen by reference to U.S. Pat. Nos. 4,784,019; 4,860,861; 5,099,711; 5,136,897 and S.A.E. Paper No. 881830 entitled "THE EATON CEEMAT (CONVERTER ENHANCED ELECTRONICALLY MANAGED AUTOMATIC TRANSMISSION)," the disclosures of which are hereby incorporated by reference in their entirety.
Such transmission systems provide an automatic mechanical transmission system utilizing a mechanical change gear transmission having a structure substantially identical to the structure of transmissions intended for manual usage, providing the advantages of a torque converter for vehicle start-ups, the advantages of nonslipping connection between the engine and transmission at higher vehicle speeds/gear ratios, and providing relatively rapid synchronization of the transmission positive jaw clutches. By providing an automatic mechanical transmission system based upon substantially the same mechanical change gear transmission utilized for manual transmission systems, manufacturing inventory and maintenance cost savings are obtained. If necessary, shifting mechanisms suitable for automatic control by solenoids or the like may be added to the transmission. An example of such a shifting mechanism may be seen by reference to above-mentioned U.S. Pat. Nos. 4,361,060 and 4,899,607 and U.S. Pat. Nos. 4,873,881; 4,722,237 and 4,445,393, the disclosures of which are hereby incorporated by reference in their entirety. A power synchronizer mechanism as disclosed in above-mentioned U.S. Pat. Nos. 4,614,126; 3,478,851 or 4,023,443 may also be added for synchronizing the transmission positive jaw clutches.
A torque converter is drivingly interposed between the drive engine and transmission. A torque converter and lock-up clutch structure is provided comprising first and second separate independently operable clutches, for coupling the torque converter driven member or turbine to the transmission input shaft and for coupling the torque converter input or impeller (i.e. the engine output) to the torque converter driven member or turbine, respectively. Preferably, the first and second clutches comprise frictional clutches.
The torque converter is drivingly interconnected between the engine and transmission only when the first coupling is engaged and the second disengaged. The torque converter is locked-up, i.e. the turbine driven directly by the engine, when the second clutch is engaged. The transmission is driven directly from the engine whenever the second clutch is engaged simultaneously with the first clutch.
When the first coupling is disengaged, regardless of the condition of the second coupling, the transmission input shaft is disconnected from the engine torque, the inertia of the torque converter, and from the inertia of the second coupling. This allows the jaw clutches to be easily disengaged while allowing the power synchronizer mechanism to act quickly (due to relatively low inertia on the input shaft), and also allowing a selected gear to be pre-engaged with the vehicle at rest and in the drive condition.
Electronic and other engine fuel control systems wherein the fuel supplied to the engine may be modulated to provide a desired engine speed, regardless of the operator's setting of the throttle pedal, are known in the prior art. Such systems may be seen by reference to above-mentioned U.S. Pat. Nos. 4,081,065; 4,361,060 and 4,792,901 and by reference to various electronic engine control standards, such as SAE J1922, SAE J1939 and ISO 11898 (which is generally similar to and compatible with SAE J1939), the disclosures of which are hereby incorporated by reference in their entirety. Other related standards include SAE J1708, J1587 and J1843, all of which are hereby incorporated by reference in their entirety.